Effect of partial substitution of Sn4+ by M4+ (M=Si, ti, and Ce) on sinterability and ionic conductivity of SnP2O7

Unlike other tetravalent metal pyrophosphates, cerium pyrophosphates have shown significant sinterability even at temperatures <500 °C. In this work, we have explored the possibility of improving sinterability of SnP2O7 by partially replacing Sn4+ ions lattice with Ce4+ions in SnP2O7. M4+-doped SnP2O7 (M=Si, Ti, and Ce) are synthesized via a solid state reaction method. It is observed that the sinterability of SnP2O7 is significantly improved by doping of 0.1 mol Ce4+. However, no such improvement is observed on partial replacement with Si4+ or Ti4+. Also, the ionic conductivity of SnP2O7 was significantly improved by Ce4+ doping and Sn0.9Ce0.1P2O7 shows >1 order of magnitude higher conductivity than that of SnP2O7. The present method of improving the sinterability and ionic conductivity of metal pyrophosphate by partial replacement of tetravalent metal ion by Ce4+ions has potential to be extended to other metal pyrophosphates such as ZrP2O7 and TiP2O7.